Septal Nectary Anatomy and Phylogeny of the Haemodoraceae

Septal nectary anatomy of members of the Haemodoraceae is described, with emphasis on nectary number and relative position within the ovary. Three types of septal nectaries are defined: infralocular, interlocular, and supralocular. The phylogenetic and possible adaptive significance of these features are assessed by adding the data to a previous cladistic analysis of the Haemodoraceae and considering cladistic patterns in terms of functional floral morphology. I hypothesize that: 1) three interlocular septal nectaries are ancestral for the Haemodoraceae, but were secondarily acquired in the genus Anigozanthos (Conostylideae) in response to selective pressure for increased nectar production for bird pollination; 2) three supralocular nectaries constitute a synapomorphy for all or most of the tribe Conostylideae, but evolved independently in the genus Dilatris of the Haemodoreae; 3) two infralocular nectaries evolved concomitantly with unique "perianth apertures" and arose via the evolution of zygomorphy and basal displacement of nectaries into the receptacular tissue; and 4) septal nectaries were independently lost in the genera Xiphidium and Phlebocarya, perhaps in response to a shift in pollination mechanism. The Hae-modoraceae are a monophyletic group consisting of 13 currently recognized genera and approximately 100 species (Anderberg and Eldenas 1991; MacFarlane et al. 1987; Simpson 1990); the monotypic Macropidia fuliginosa has recently been reclassified as a member of the genus Anigozanthos by Anderberg and Eldenas (1991), a viewpoint with which I wholly agree. Members of the Haemodoraceae are rhizomatous to stoloniferous herbs, with equitant, unifacial leaves and mostly cymose inflorescences and have distributions spanning Australia, South Africa, South and Central America, and eastern North America. The family exhibits considerable diversity in floral morphology. Flowers range in size from approximately 5 mm long in the bee-pollinated genera Xiphidium (South and Central America) and Phlebocarya (southeastern Australia) to over 6 cm long in species of the bird-pollinated Anigozanthos (southwestern Australia). Flowers may be either actinomorphic or zygomorphic, enantiostylous or symmetrically-styled, glabrous or densely tomentose (ranging in color from white, yellow, green, orange, red, to black); the perianth can be either imbricate or valvate; stamen number is 6, 3, or 1; ovary position is superior, half-inferior, or inferior; locule number and fertile carpel number is either 3 or 1; and ovules and seeds may be 1, 2, 4, 5-7, or indefinite in number, epitropous or hypotropous in position, and considerably variable in shape and size (see Simpson 1990). I recently analyzed the phylogenetic relationships of genera and species complexes within the Haemodoraceae and proposed some changes in classification (Simpson 1990). In order to understand better the evolution of the diverse floral morphology in the group and to help resolve incompatibilities of certain hypotheses of character evolution, I have initiated studies of floral anatomy, ovary development, and ovule/seed development in the family. This paper describes observations on the anatomy and spatial relationship of septal nectaries in the Haemodoraceae (and near outgroups) and the phylogenetic significance of these new data. More detailed anatomical descriptions of septal nectary epithelial cells, subepithelial cells, and surrounding vasculature and ergastic substances will appear in another publication. Dahlgren and Clifford (1982) reviewed the occurrence of floral nectaries in monocotyledons, relying primarily on the work by Daumann (1970). The three major types of nectaries in monocots that they defined are: 1) perigonal-nectaries at the adaxial bases of tepals; 2) androecial-nectaries on filaments of stamens or staminodes; and 3) septal-nectaries found in the septal regions of the gynoecium. Rare types of monocot nectaries include those found at style bases, stigmas, surface of carpels or ovary, and nectariferous disks. Septal nectaries are by far the most common type found in monocotyledons and are entirely lacking in dicots (Schmid 1985). Septal nectaries are nectar-se-